Pressure sensitive copying sheet

ABSTRACT

A PRESSURE SENSITIVE COPYING SHEET HAVING AS A COLOR FORMER A COMPOUND REPRESENTED BY THE FOLLOWING FORMULA:   3-(R1-N(-R2)-),7-PHENYL-SPIRO(PHTHALAN-1,9&#39;&#39;-XANTHENE)   WHEREIN R1 AND R2 EACH IS AN ALKYL GROUP HAVING 1 TO 5 CARBON ATOMS.

United States Patent 3,669,710 PRESSURE SENSITIVE COPYING SHEET Shiro Kimura, Teruo Kobayashi, and Sadao Ishige, Kanagawa, Japan, assiguors to Fuji Photo Film C0., Ltd., Kanagawa, Japan No Drawing. Filed May 7, 1970, Ser; No. 35,596 Claims priority, application Japan, May 7, 1969, 44/34,968 Int. Cl. B41m /22 US. Cl. 117--36.2 Claims ABSTRACT OF THE DISCLOSURE A pressure sensitive copying sheet having as a color former a compound represented by the following formula:

wherein R and R each is an alkyl group having 1 to 5 carbon atoms.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a pressure sensitive copying sheet, and more particularly to a pressure sensitive copying sheet using as a color former a compound represented by the above general formula.

DESCRIPTION OF THE PRIOR ART An ordinary pressure sensitive copying sheet consists of an upper sheet coated with an electron donating, colorless organic compound (hereinafter referred to as a color former) which is dissolved in an oil and enclosed in microcapsules, and a lower sheet coated with an electron accepting substance (hereinafter referred to as a solid acid) together with a suitable binder. The sheets are superimposed in such a manner that the coating surfaces are contacted. When the copying paper is locally pressurized by either handwriting or typewriting, the microcapsules in the pressurized portion are ruptured and the color former is absorbed in the solid acid, whereby distinct color copying images are formed. In this case, an intermediate sheet coated with the microcapsules on one side thereof and with the solid acid on the other side may be inserted between the upper sheet and the lower sheet. In another embodiment of a pressure sensitive copying sheet, the microcapsules and the solid acid may be coated simultaneously on one side of a support.

The above-identified solid acid includes acid clay, active clay, attapulgite, bentonite, organic acids and phenolic resins; and the color former includes rhodamine B lactone, rhodamine anilinolactarn, crystal violet lactone, malachite green lactone and benzoyl leucomethylene blue.

3,669,710 Patented June 13, 1972 There has never been known any color former which is capable of forming pure red images instantly when contacted with the solid acid, although orange red colorforming compounds have been known, such as compound A described in Senryo to Yakuhin Dyes and Chemicals), vol. 9, No. 4, page 130, and compound B described in Japanese patent publication No. 6,993/69, which are represented by the following formulae:

N- /O N /o on; s i C2415 \c \0 CH3 Compound A Compound B SUMMARY OF THE INVENTION The present inventors have discovered that a pressure sensitive copy sheet having desirable properties can be obtained by using as the color former a compound represented by the following formula:

wherein R and R each is an alkyl group having 1 to 5 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The above compound maybe microcapsulated by a coacervation method such as that described in US. Pat. No.

2,800,457 and then coated on a support such as a paper. The thus-prepared pressure sensitive copying sheet has excellent stability under atmospheric conditions prior to the rupturing of the microcapsules, that is, the compound contained in the microcapsules is not colored or decomposed by atmospheric conditions and therefore the color forming properties of the copying sheet are not destroyed or decreased before its use.

The copying sheet is able to form pure red images having a higher density when contacted with the electron accepting substance or solid acid. Thus, the formed color dye is more excellent in light, heat and water resisting properties. Further, the color former of this invention may be used together with conventional yellow and blue color formers to give the various pressure-sensitive copying sheets capable of forming black or blue-black images without desensitizing the color formers.

The compound represented by the above general formula, used for the pressure sensitive copying sheet of this invention, may be prepared by, for example, reacting o-(4- dialkyl amino-2-hydroxybenzoyl) benzoic acid with pphenyl phenol in 50-98% concentrated sulfuric acid at a temperature of from 30 to 60 C. for a period of time of from 1 to 24 hours and neutralizing the resulting reaction mixture.

In the preparation examples described below, various methods for the production of typical compounds represented by the above general formula are shown.

PREPARATION EXAMPLE 1 Production of color former (1), which is represented by the general formula above when both R and R are ethyl groups.

15.7 g. of o-(4-diethyl amino-Z-hydroxybenzoyl)benzoic acid and 8.5 g. of p-phenyl phenol were dissolved in 30 cc; of 85% sulfuric acid and the solution was reacted on a steam bath for 3 hours. The reaction mixture was then poured into ice-water and precipitated color former salt was neutralized with an aqueous solution of sodium hydroxide. The neutralized product was dissolved in toluene, washed with water and the solution was concentrated under reduced pressure to give 14.0 g. of the desired product melting at 216-218 C., in colorless crystalline form.

PREPARATION. EXAMPLE 2 Production of color former (2), which is represented by the general formula above when both R and R are methyl groups.

13.5 g. of o-(4-dimethyl amino-2-hydroxybenzoyl)- benzoic acid, and 8.5 g. of p-phenyl phenol were reacted in the same manner as described in Preparation Example 1 above, and 13 g. of the desired product melting at 277- 279 C. was obtained in a colorless crystalline form.

In the production of the pressure sensitive copying sheet of the present invention, in which the compound represented by the above general formula is used as the color former, any known process for the production of the microcapsules may be employed, including those processes described in US. Pat. Nos. 2,548,366, 2,800,457 and 2,800,458, i.e., whereby the phenomenon of the complex coacervation method is being utilized to make the microcapsules.

Therefore, the sole characteristic feature of the present invention is to use the compound represented by the above formula as the color former. The properties of the resulting pressure sensitive sheet of this invention are not dependent on the method by which the sheet is fabricated. Generally, the color former may be used in an amount from 0.5 to by weight, based on the weight of the organic solvent in which the color former is dissolved.

As the solid acid used for the production of this pressure sensitive copying sheet, active clay substances such as acid clay, active clay, attapulgite, zeolite or bentonite, and organo-acidic substances such as succinic acid, tannic acid, gallic acid, pentachloro-phenol, or phenolic resin are generally used.

The organic solvent used for dissolving the color former may be benzene chloride, diphenyl chloride etc.

The following examples illustrate pressure sensitive copying sheets of this invention using typical color formers represented by the general formula above.

4 Example 1 3 g. each of color formers (1) and (2) were treated in the following manner.

Each color former was dissolved in g. of trichlorodiphenyl, and the solution was emulsified with the addition of 20 g. of gum arabic and g. of water at 50 C. Into the emulsified solution, 20 g. of gelatin and 160 g. of water were added and the pH of the resulting mixture was adjusted to 5 by adding acetic acid with stirring. Then 500 g. of water was added to the mixture to initiate the coacervation to thereby form a thick liquid film of gelatin-gum arabic around the droplets of the color forming compound dissolved in the trichlorodiphenyl. Then the pH of the mixture was adjusted to 4.4 and 3.8 g. of 37% formaline was added to the mixture to harden the gelatin-gum arabic film to microencapsulate the droplets. The mixture was then cooled to 10 C. and the pH was adjusted to 9 with added sodium hydroxide solution. The resulting mixture was allowed to stand for 5-6 hours to complete the microencapsulation.

The thus-formed encapsulated solution was coated on paper by means of a roll-coating or an air-knife coating method, and the coated paper was dried. The thus-prepared coated paper was used as an upper sheet and was faced to a lower sheet coated wtih acid clay, attapulgite, zeolite or bentonite clay, and pressure from a pencil or typewriter key was applied on the surface of the upper sheet. In this manner a color image was instantly formed on the surface of the lower sheet where the pressure or impact was applied. The color thus formed was pure red regardless of the kind of the clay used.

The formed color was exposed to direct sun light for a long period of time or soaked in water, and there was substantially no fading of color on the sheet.

Further, when a lower sheet coated with an organoacidic substance such as succinic acid, gallic acid, p-toluene sulfonic acid pentachloro-phenol or phenolic resin were used instead of a clay-coated lower sheet, a pure red color was also formed.

The upper sheet coated with the color forming compound was heated at 100 C. for 20 hours, or exposed to direct sun light for a long period of time but no decrease of the color forming capacity of the sheet was observed.

Example 2 An upper sheet was prepared in the same manner as described in Example 1 but, instead, using 10.0 g. of color former (1) together with known color formers (0.5 g. of benzoyl-leucomethylene blue, 0.7 g. of malachite green lactone, 0.4 g. of crystal violet lactone and 1.5 g. of w-(2-hydroxybenzal) acetonephenone). The thus-prepared upper sheet was contacted with a lower sheet coated with an electron accepting substance, and pressure was applied thereon. In this manner, a black color was rapidly formed on the lower sheet.

Example 3 An upper sheet was prepared in the same manner as described in Example 1, but, instead, using 0.6 g. of color forming compound (1) together with known color formers (0.5 g. of benzoyl leucomethylene blue, 2.0 g. of crystal violet lactone and 0.4 g. of w(2-hydroxybenzal) acetophenone). The thus-prepared sheet was contacted with a lower sheet, and pressure was applied. In this manner, a blue-black color instantly appeared on the lower sheet.

Example 4 Mircocapules containing liquid prepared in the same manner as described in Example 1 were coated on the underside of an intermediate sheet and an electron accepting substance was coated on one side of the sheet. Several intermediate sheets so prepared were inserted between an upper sheet and a lower sheet prepared in the same manner as described in Example 1. Pressure was then applied on the upper sheet and a pure red color ap peared on every intermediate sheet and lower sheet.

Example 5 Microencapsulated color formers prepared in the same manner as in Example 1 were coated on paper on which an electron accepting substance had been previously coated. The thus-prepared pressure sensitive copying sheet was laid under ordinary paper, and pressure was applied onto the paper. A pure red color appeared on the pressure sensitive copying sheet.

What is claimed is:

1. A pressure sensitive copying sheet comprising a support having coated thereon a layer containing microcapsules, said microcapsules containing a colorless compound dissolved in oil and represented by the formula:

wherein R and R each is an alkyl group having from 1 to 5 carbon atoms, said compound being capable of forming a color dye when contacted with an electron accepting solid acid.

2. The pressure sensitive copying sheet as in claim 1 wherein said compound is a member selected from the group consisting of 3-dimethylamino-7-phenol-fluoran and 3-diethylamino-7-phenyl-fluoran.

3. The pressure sensitive copying sheet as in claim 1 wherein said microcapsules are coated on one side of said support together with said solid acid.

4. The pressure sensitive copying sheet as in claim 1 wherein said microcapules are coated on the opposite surface of said support coated with said solid acid.

5. A pressure sensitive copying sheet comprising an upper sheet having coated thereon a layer containing microcapsules containing a colorless compound dissolved in oil and represented by the formula:

wherein R and R each is an alkyl group having from 1 to 5 carbon atoms, and a lower sheet having coated thereon a solid acid layer.

6. The pressure sensitive copying sheet as in claim 3 wherein said compound is a member selected from the group consisting of 3-dimethylamino-7-phenyl-fluoran and 3-diethylamino-7-phenyl-fiuoran.

7. The pressure sensitive copying sheet as in claim 3 wherein said solid acid is a member selected from the group consisting of acid clay, active clay, attapulgite, bentonite and phenolic resin.

8. The pressure sensitive copying sheet as in claim 1 wherein said compound is contained in microcapsules together with another colorless compound.

9. The pressure sensitive copying sheet as in claim 1, wherein said microcapsules contain from 0.5 to 10% by weight of said compound, based on the weight of said oil.

10. The pressure sensitive copying sheet as in claim 8, wherein said another colorless compound is selected from the group consisting of benzoyl-leucomethylene blue, malachite green lactone, crystal violet lactone and w-(Z- hydroxybenzal) acetophenone.

References Cited UNITED STATES PATENTS 3,514,310 5/1970 Kimura et a1. 11736.2 3,501,331 3/1970 Kimura et a1 l1736.8 3,506,471 4/1970 Kimura et al. 11736.2 3,514,311 5/1970 Katayama et a1 ll7-36.2

MURRAY KATZ, Primary Examiner US. Cl. X.'R. 

